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It's Official: Sea Lice From Salmon Farms Infecting Wild Stock

A new study is the first to show a potential role of salmon farms in sea lice transmission to juvenile sockeye salmon during their critical early migration to the sea.

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The study also recorded high lice levels on juvenile sockeye near a farmed salmon processing plant in the Georgia Strait, heightening concern for the full potential impact of the salmon farm industry on wild salmon in this region.

The British Columbia Salmon Farmers Association says that sea lice on farmed salmon are monitored and managed to minimize possible transfer to wild populations. This work is audited by provincial authorities and is a condition of farm license.

Every salmon farm is monitored monthly and, during the spring months when juvenile salmon may be traveling past the farms, fish are inspected at least once every two weeks. If the average number of motile sea lice reaches three per fish, veterinarians prescribe the medication emamectin benzoate, called SLICE, to remove the lice from all salmon on the farm, the association says. The chemical is delivered to salmon through fish feed.

Health Canada says its stringent conditions regarding the use of SLICE assures the safety and quality of the products entering the consumer market. The agency says, "There are no health risks associated with the consumption of SLICE-treated salmon."

Fisheries and Oceans Canada says there is no risk to human health from eating salmon infected with sea lice. "Sea lice live on the outside of the fish and feed on the slippery mucus on the skin of the fish. They would not affect human health if eaten, and usually the lice fall off or are cleaned off during harvesting or processing activities before the fish even reaches the consumer," the agency says.

Sea lice from salmon farms are one more stressor for sockeye already subjected to multiple human impacts. Yet lice are not the worst of the stressors the young salmon face.

The authors say that risks to juvenile sockeye from open net-pen salmon farms can be much more easily mitigated than changes to ocean conditions from climate change and ocean acidification.

Recommendations include removal of farm salmon from the migration routes of juvenile sockeye, and transition of salmon farms to closed-containment facilities.

Cycles of abundance vary greatly for Fraser River sockeye returning from the sea to spawn in the river where they themselves were spawned. The returning population of Fraser River sockeye in 2009 was a very low 1.37 million, just 13 percent of the pre-season forecast. But the number of sockeye returning in 2010 was around 30 million, the largest sockeye run in 97 years.

Copyright Environment News Service (ENS) 2011. All rights reserved.

 
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